Foreign Minister Manouchehr Mottaki said that following its referral to the UN Security Council, Iran no longer had any obligations towards the additional protocol, an agreement that gives international inspectors the right to make short-notice visits to Iran's nuclear sites.

"Yesterday we had two options. One was the option of resistance and the other was surrender," he said. "We chose resistance."

The protocol also means Iran will end its voluntary suspension of industrial-scale uranium enrichment.

Uranium enrichment is a process that creates fuel for nuclear reactors and, potentially, for a nuclear bomb.

Iran denies it has been concealing efforts to develop nuclear weapons, maintaining its programme is only for producing energy and does not have a military aim.

The BBC's Frances Harrison says that without the protocol the IAEA will be more restricted in its work, which was already difficult because of lack of Iranian co-operation.

US President George W Bush said on Saturday the referral to the UN Security Council "sent a clear message to the regime in Iran" that it could not gain nuclear weapons.

The move to report Tehran, agreed by 27 of the 35 states on the International Atomic Energy Agency (IAEA), could lead to possible sanctions against Iran.

'New situation'

On Saturday, Iranian deputy nuclear negotiator Javad Vaiedi appeared to cast doubt on the compromise deal with Russia, saying it was not clear how the proposal could be considered.